As a technique for determining a frequency to be used for power reception, from among one or more frequency candidates, the following has been known. A certain terminal (a terminal to receive power) receives first information including one or more frequency candidates from another terminal. The terminal to receive power receives a microwave which is transmitted, as a frequency candidate included in the first information, from the other terminal, and measures DC energy which is obtained by performing DC conversion on the energy of the microwave. The terminal to receive power identifies an optimum frequency at which the DC energy becomes maximum, among the one or more frequency candidates, and transmits, to the other terminal, second information including the identified optimum frequency.
In this technique, when a separate communication system uses a frequency in a bandwidth including the above frequency candidates, the terminal to receive power may receive radio waves transmitted from the separate communication system. In this case, the terminal to receive power cannot accurately measure the energy of radio waves received from the other terminal, and thus, cannot identify the optimum frequency.